This article describes a soft suction cup end effector with squid-inspired suction generation and an octopusinspired cup design that uses a dielectric elastomer actuator (DEA) to generate suction for adhesion. The fabrication process for the end effector is described in detail, and a mechanical model for generated pressure differential as a function of voltage is presented. When actuated, the DEA exerts an electrostatic stress on the walls of the end effector, resulting in pressure reduction in its water-filled cavity. The actuator is soft, flexible, and creates suction without a reliance on typical DEA elements such as rigid supporting structures and elastomer prestrain. It does not require net fluid flux out of the sucker, allowing faster attachment and easier release. It can be actuated underwater and has been validated with pull-off tests. The sucker generates a pressure differential of 3.63-0.07 kPa (-SD) when driven at 10.75 kV in water and should reach a 4.90 kPa pressure differential when energized at its theoretical failure point of 12.4 kV. Data normalized by the input voltage show that 90% of the maximum pressure differential can be achieved within 50 ms of voltage application. Weighing less than 30 g in air, this elastomer end effector is capable of pulling with a force of 8.34-0.10 N (-SD) and reversibly lifting 26.7 times its own mass underwater when actuated at 10.75 kV.

No abstract

Recent efforts in soft-body control have been hindered by the infinite dimensionality of soft bodies. Without restricting the deformation space of soft bodies to desired degrees of freedom, it is difficult, if not impossible, to guarantee that the soft body will remain constrained within a desired operating range. In this article, we present novel modeling and fabrication techniques for leveraging the reorientation of fiber arrays in soft bodies to restrict their deformation space to a critical case. Implementing this fiber reinforcement introduces unique challenges, especially in complex configurations. To address these challenges, we present a geometric technique for modeling fiber reinforcement on smooth elastomeric surfaces and a two-stage molding process to embed the fiber patterns dictated by that technique into elastomer membranes. The variable material properties afforded by fiber reinforcement are demonstrated with the canonical case of a soft, circular membrane reinforced with an embedded, intersecting fiber pattern such that it deforms into a prescribed hemispherical geometry when inflated. It remains constrained to that configuration, even with an additional increase in internal pressure. Furthermore, we show that the fiber-reinforced membrane is capable of maintaining its hemispherical shape under a load, and we present a practical application for the membrane by using it to control the buoyancy of a bioinspired autonomous underwater robot developed in our lab. An additional experiment on a circular membrane that inflates to a conical frustum is presented to provide additional validation of the versatility of the proposed model and fabrication techniques.

No abstract